Semiconductor chip manufacturing method, semiconductor chip, semiconductor device manufacturing method, and semiconductor device

ABSTRACT

The invention provides a semiconductor chip manufacturing method, including a step of forming a front-surface-side concave portion in a semiconductor substrate having a front surface and a rear surface, a functional device being formed on the front surface, the front-surface-side concave portion being formed in the front surface and having a predetermined depth smaller than a thickness of the semiconductor substrate; a dummy plug forming step of supplying nonmetallic material into the front-surface-side concave portion and embedding a dummy plug made of the nonmetallic material; a thinning step of removing a part of the rear surface of the substrate and thinning the semiconductor substrate so that the thickness of the semiconductor substrate becomes smaller than the depth of the front-surface-side concave portion and so that the front-surface-side concave portion is formed into a through-hole; a dummy plug removing step of removing the dummy plug; and a step of supplying metallic material into the through-hole and forming a penetration electrode.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a semiconductor chip that has a through-holepenetrating in its thickness direction, a method for manufacturing thesemiconductor chip, a semiconductor device that has a semiconductor chiphaving a through-hole penetrating in its thickness direction, and amethod for manufacturing the semiconductor device.

2. Description of Related Art

A multichip module (MCM) is known as a semiconductor device having aplurality of semiconductor chips. In the multichip module, an attempthas been made to reduce the mounting area of a semiconductor device bystacking a plurality of semiconductor chips together on a wiringsubstrate in the semiconductor device. In some of the thus structuredsemiconductor devices, a penetration electrode is provided in athrough-hole penetrating through semiconductor chips in the thicknessdirection, and a longitudinal electrical connection is achieved by thispenetration electrode.

FIG. 13A to FIG. 13H are diagrammatic sectional views for explaining aconventional method for manufacturing a semiconductor chip having apenetration electrode. This method is disclosed by Japanese translationof International Application (Kohyo) No. 2000-510288.

A hard mask 103 having an opening 103 a in which a region beside afunctional device 101 is exposed is formed on a surface of asemiconductor wafer (hereinafter, referred to simply as “wafer”) W onone surface (hereinafter, referred to as “front surface”) of which thefunctional device 101 is provided.

Thereafter, a front-surface-side concave portion 102 that has a depthsmaller than the thickness of the wafer W is formed in the region besidethe functional device 101 by carrying out reactive ion etching (RIE)where the hard mask 103 is used as a mask, whereafter a contact hole 103b in which a predetermined part of the functional device 101 is exposedis formed in the hard mask 103.

Thereafter, an insulating film 104 made of silicon oxide is formed onthe exposed surface in the opening 103 a and the exposed surface in thefront-surface-side concave portion 102. FIG. 13A shows this state.

Thereafter, an electroconductive diffusion-preventing film 105 is formedon the whole of the front surface of the wafer W that has undergone theforegoing steps (see FIG. 13B), and a seed layer (not shown) is formedon the diffusion preventing film 105. The inside of the opening 103 a,the inside of the contact hole 103 b, and the inside of thefront-surface-side concave portion 102 are then filled with a metal film106 made of copper by carrying out electrolytic plating where the seedlayer is used a seed. Accordingly, the metal film 106 is electricallyconnected to the functional device 101 through the contact hole 103 b.FIG. 13C shows this state.

Thereafter, a part of the metal film 106 and a part of the diffusionpreventing film 105 are removed, except for the inside of thefront-surface-side concave portion 102, the opening 103 a, and thecontact hole 103 b and except for a predetermined region having apattern that makes a connection between the inside of the opening 103 aand the inside of the contact hole 103 b. FIG. 13D shows this state.

Thereafter, a UBM layer 107 and a bump 108 are formed on the metal film106 outside the front-surface-side concave portion 102, the opening 103a, and the contact hole 103 b. The UBM layer 107 lies between the metalfilm 106 and the bump 108. FIG. 13E shows this state.

Thereafter, the front surface of the wafer W is stuck onto a supporter(not shown), and the rear surface Wr of the wafer W is mechanicallyground, whereby the wafer W is thinned. As a result, thefront-surface-side concave portion 102 becomes a through-hole 112, andthe metal film 106 is exposed to the rear surface Wr of the wafer W. Themetal film 106 in the front-side concave portion 102 and in the opening103 a becomes a penetration electrode 109. The remainder of the metalfilm 106 integral with the penetration electrode 109 functions as awiring member 110 through which the penetration electrode 109 and thefunctional device 101 are electrically connected to each other. FIG. 13Fshows this state.

A grinding damage layer, which has grinding marks or damage receivedwhen ground, exists on the rear surface Wr of the wafer W. To remove thegrinding damage layer, the rear surface Wr of the wafer W is subjectedto dry etching by approximately Sum. At this time, the penetrationelectrode 109, the diffusion preventing film 105, and the insulatingfilm 104 are hardly etched, and jut from the rear surface Wr of thewafer W. FIG. 13G shows this state.

Thereafter, a rear-surface-side insulating film 111 made of siliconoxide is formed on the whole of the rear surface Wr of the wafer W, andthen a part of the insulating film 111, with which the penetrationelectrode 109, the diffusion preventing film 105, and the insulatingfilm 104 are covered, is ground, is removed, and is exposed (see FIG.13H). Thereafter, the wafer W is cut into semiconductor chips, eachhaving the penetration electrode 109.

Semiconductor chips obtained according to the manufacturing methoddescribed above are stacked together in the longitudinal direction, andthe bump 108 of each of the adjoining semiconductor chips is joined tothe penetration electrode 109 of the adjoining semiconductor chip, thepenetration electrode 109 being exposed at the rear surface Wr of thewafer W, whereby the semiconductor chips can be electrically connectedtogether. Therefore, the wiring length can be shortened. In the thusstructured semiconductor device, the mounting area with respect to, forexample, the wiring substrate is small.

However, according to the conventional method for manufacturing asemiconductor chip that has a penetration electrode 109, not only thewafer W but also the metal film 106 (the penetration electrode 109) isground when the rear surface Wr of the wafer W is ground (see FIG. 13F).Therefore, the copper forming the metal film 106 reaches to a deep partof the wafer W from the rear surface Wr of the wafer W because ofdiffusion, and remains in the wafer W even if a grinding damage layer isremoved (see FIG. 13G). Thus, the wafer W is contaminated, and theproperties of the semiconductor chip are deteriorated.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method formanufacturing a semiconductor chip capable of restraining the metalcontamination of a semiconductor substrate caused by forming apenetration electrode.

It is another object of the present invention to provide a semiconductordevice having a semiconductor chip excellent in properties while havinga penetration electrode.

It is still another object of the present invention to provide a methodfor manufacturing a semiconductor device capable of restraining themetal contamination of a semiconductor chip caused by forming apenetration electrode.

It is still another object of the present invention to provide asemiconductor chip capable of excellently transmitting a light signalthrough a through-hole formed in a semiconductor substrate and toprovide a method for manufacturing the semiconductor chip.

A method for manufacturing a semiconductor chip according to a firstaspect of the present invention includes a step of forming afront-surface-side concave portion in a semiconductor substrate having afront surface and a rear surface, a functional device being formed onthe front surface, the front-surface-side concave portion being formedin the front surface and having a predetermined depth smaller than athickness of the semiconductor substrate; a dummy plug forming step ofsupplying nonmetallic material into the front-surface-side concaveportion and embedding a dummy plug made of the nonmetallic material inthe front-surface-side concave portion; a thinning step of, subsequentto the dummy plug forming step, removing a part of the rear surface ofthe semiconductor substrate and thinning the semiconductor substrate sothat the thickness of the semiconductor substrate becomes smaller thanthe depth of the front-surface-side concave portion and so that thefront-surface-side concave portion is formed into a through-hole thatpenetrates the semiconductor substrate; a dummy plug removing step ofremoving the dummy plug provided in the through-hole; and a step of,subsequent to the dummy plug removing step, supplying metallic materialinto the through-hole and forming a penetration electrode thatestablishes an electrical connection between a front surface side and arear surface side of the semiconductor substrate and that iselectrically connected to the functional device.

According to this invention, the dummy plug made of nonmetallic materialis provided and metallic material is not provided in thefront-surface-side concave portion (through-hole) when the thinning stepis executed. Therefore, metal atoms are never diffused from the rearsurface of the semiconductor substrate into the semiconductor substratewhen ground, for example, even if the thinning step is to physicallygrind the rear surface of the semiconductor substrate. In other words,the metal contamination of the semiconductor substrate caused by theformation of the penetration electrode can be prevented. Therefore,according to the manufacturing method of the present invention, asemiconductor chip that has less metal contamination and that exhibitsexcellent properties can be produced while having a penetrationelectrode.

A semiconductor chip that has a penetration electrode that penetrates asemiconductor substrate in the thickness direction can be obtained bysupplying metallic material into a through-hole from which a dummy plughas been removed. This penetration electrode makes it possible toestablish an electrical connection in a short distance between the frontsurface side and the rear surface side of the semiconductor substrate.

The nonmetallic material forming the dummy plug may be a polymer, forexample.

If the thinning step is to physically grind the rear surface of thesemiconductor substrate, this semiconductor chip manufacturing methodmay additionally include a step of, subsequent to the thinning step,removing a grinding damage layer having grinding marks or damage causedby the thinning step.

Preferably, this semiconductor chip manufacturing method includes a stepof, subsequent to the dummy plug removing step and prior to thepenetration electrode forming step, forming an insulating film on theinner wall of the through-hole. In this case, in the resultingsemiconductor chip, an insulating film is interposed between thepenetration electrode and the semiconductor substrate, and thisinsulating film establishes electrical insulation between thepenetration electrode and the semiconductor substrate.

Preferably, this semiconductor chip manufacturing method includes a stepof, subsequent to the dummy plug removing step and prior to thepenetration electrode forming step, forming a diffusion preventing film,which prevents metal atoms from being diffused from the inside of thethrough-hole into the semiconductor substrate, on the inner wall of thethrough-hole. In this case, in the resulting semiconductor chip, adiffusion preventing film is interposed between the penetrationelectrode and the semiconductor substrate, and this diffusion preventingfilm can prevent metal atoms from being diffused from the penetrationelectrode into the semiconductor substrate and can prevent adeterioration in the properties of the semiconductor chip.

The penetration electrode forming step may include, for example, a stepof supplying metallic material into the through-hole by electrolyticplating. In this case, a step of forming a seed layer on the inner wallof the through-hole may be carried out before supplying the metallicmaterial.

The semiconductor chip manufacturing method of the present invention mayfurther include a step of, subsequent to the dummy plug forming step andprior to the dummy plug removing step, forming a wiring member thatcomes into contact with an exposed surface of the dummy plug on thefront surface side of the semiconductor substrate and that iselectrically connected to the functional device.

According to this arrangement, since the wiring member is formed to comeinto contact with the exposed surface of the dummy plug on the frontsurface side of the semiconductor substrate, a penetration electrodeelectrically connected to the wiring member is formed by supplyingmetallic material into the through-hole from which the dummy plug hasbeen removed. Since the wiring member is electrically connected to thefunctional device, the penetration electrode electrically connected tothe functional device can be easily produced according to this method.

The dummy plug forming step may include a photosensitive resin fillingstep of filling an inside of the front-surface-side concave portion withphotosensitive resin having nonconductivity as the nonmetallic materialso as to form the dummy plug made of the photosensitive resin and anexposure step of exposing the dummy plug to light so that apredetermined outer peripheral part of the dummy plug along a wholeinner wall surface of the front-surface-side concave portion isinsoluble in a predetermined etching medium and so that a central partof the dummy plug inward from the outer peripheral part is soluble inthe predetermined etching medium. In this case, the dummy plug removingstep may include a development step of removing the central part of thedummy plug according to etching using the predetermined etching medium.

According to this arrangement, the entire dummy plug is not removed bythe development step, and the outer peripheral part of the dummy plugalong the whole inner wall surface of the front-surface-side concaveportion is left. Since the dummy plug is made of insulating material,the outer peripheral part of the dummy plug that remains there withoutbeing removed is interposed between the penetration electrode and thesemiconductor substrate, and serves as an insulating film thatestablishes electrical insulation between the penetration electrode andthe semiconductor substrate in the resulting semiconductor chip.

The insulating film can be formed to have a desired thickness bycontrolling the exposure area of the dummy plug in the exposure step.Therefore, a thick insulating film having sufficient nonconductivity canbe easily formed.

The photosensitive resin may be so-called positive type photosensitiveresin which is insoluble in a predetermined etching medium, and anexposed part of which is soluble therein, or may be so-called negativetype photosensitive resin which is soluble in a predetermined etchingmedium, and an exposed part of which is insoluble therein.

To restrict an exposure area, a resist with a predetermined pattern maybe used. The exposure area may be restricted by a substance other thanthe resist. For example, if a front-surface-side concave portion isformed by reactive ion etching using a hard mask having an opening, thisfront-surface-side concave portion will have a width slightly greaterthan the width of the opening. Therefore, the hard mask is projectedinward slightly from the edge of the front-surface-side concave portion.The exposure area with respect to the photosensitive resin (dummy plug)in the front-surface-side concave portion may be restricted by usingthis projection of the hard mask.

A semiconductor device manufacturing method according to a second aspectof the present invention includes a producing step of producing aplurality of semiconductor chips and a stacking step of stacking theplurality of semiconductor chips together. The semiconductor chipproducing step includes a step of forming a front-surface-side concaveportion in a semiconductor substrate having a front surface and a rearsurface, a functional device being formed on the front surface, thefront-surface-side concave portion being formed in the front surface andhaving a predetermined depth smaller than a thickness of thesemiconductor substrate; a dummy plug forming step of supplyingnonmetallic material into the front-surface-side concave portion andembedding a dummy plug made of the nonmetallic material in thefront-surface-side concave portion; a thinning step of, subsequent tothe dummy plug forming step, removing a part of the rear surface of thesemiconductor substrate and thinning the semiconductor substrate so thatthe thickness of the semiconductor substrate becomes smaller than thedepth of the front-surface-side concave portion and so that thefront-surface-side concave portion is formed into a through-hole thatpenetrates the semiconductor substrate; a dummy plug removing step ofremoving the dummy plug provided in the through-hole; and a step of,subsequent to the dummy plug removing step, supplying metallic materialinto the through-hole and forming a penetration electrode thatestablishes an electrical connection between a front surface side and arear surface side of the semiconductor substrate and that iselectrically connected to the functional device.

The metal contamination of the semiconductor chip caused by theformation of the penetration electrode can be prevented according to thestep of producing a plurality of semiconductor chips. Therefore,according to this semiconductor device manufacturing method, it ispossible to obtain a semiconductor device that has semiconductor chipseach of which has a penetration electrode and is small in metalcontamination.

The penetration electrode can realize an electrical connection in ashort distance between a functional device of one of two adjoiningsemiconductor chips stacked together and a functional device of theother semiconductor chip.

A method for manufacturing a semiconductor device according to a thirdaspect of the present invention includes a step of forming afront-surface-side concave portion in a first semiconductor substratehaving a front surface and a rear surface, a functional device beingformed on the front surface, the front-surface-side concave portionbeing formed in the front surface and having a predetermined depthsmaller than a thickness of the first semiconductor substrate; a dummyplug forming step of supplying nonmetallic material into thefront-surface-side concave portion and embedding a dummy plug made ofthe nonmetallic material in the front-surface-side concave portion; astacking step of stacking the first semiconductor substrate on a secondsemiconductor substrate while causing the front surface of the firstsemiconductor substrate in which the dummy plug is formed to face onesurface of the second semiconductor substrate; a thinning step ofremoving a part of the rear surface of the first semiconductor substratestacked on the second semiconductor substrate and thinning the firstsemiconductor substrate so that the thickness of the first semiconductorsubstrate becomes smaller than the depth of the front-surface-sideconcave portion and so that the front-surface-side concave portion isformed into a through-hole that penetrates the first semiconductorsubstrate; a dummy plug removing step of, subsequent to the thinningstep, removing the dummy plug provided in the through-hole; and ametallic material supplying step of, subsequent to the dummy plugremoving step, supplying metallic material into the through-hole andforming a penetration electrode that establishes an electricalconnection between a front surface side and a rear surface side of thefirst semiconductor substrate and that is electrically connected to thefunctional device.

According to this invention, the dummy plug made of nonmetallic materialis provided and metallic material is not provided in thefront-surface-side concave portion (through-hole) when the thinning stepis executed. Therefore, metal atoms are never diffused from the rearsurface of the first semiconductor substrate into the firstsemiconductor substrate when ground, for example, even if the thinningstep is to physically grind the rear surface of the first semiconductorsubstrate. In other words, the metal contamination of the firstsemiconductor substrate caused by the formation of the penetrationelectrode can be prevented.

Therefore, according to this semiconductor device manufacturing method,it is possible to produce a semiconductor device having a semiconductorchip (the first semiconductor substrate or a semiconductor substrateformed by cutting the first semiconductor substrate) that has apenetration electrode and less metal contamination.

According to this semiconductor device manufacturing method, the firstsemiconductor substrate is thinned while being stacked on the secondsemiconductor substrate, so as to form a penetration electrode.Therefore, there is no need to stack the first semiconductor substrate,which has undergone the thinning step, on the second semiconductorsubstrate.

This semiconductor device manufacturing method may further include astep of, prior to the stacking step, forming a dummy bump that juts fromthe front surface of the first semiconductor substrate and that comesinto contact with the dummy plug. In this case, the second semiconductorsubstrate may include a wiring member provided on the one surface of thesecond semiconductor substrate. In this case, the stacking step mayinclude a dummy bump contact step of bringing the dummy bump intocontact with the wiring member of the second semiconductor substrate anda step of disposing tracing material in such a manner as to cover aperiphery of the dummy bump being in contact with the wiring member ofthe second semiconductor substrate. In this case, the dummy plugremoving step may include a step of removing the dummy bump. In thiscase, the metallic material supplying step may include a step ofsupplying metallic material to a space that communicates with thethrough-hole and that is defined by the tracing material and forming abump that is formed integrally with the penetration electrode and thatjuts from the front surface of the first semiconductor substrate.

According to this arrangement, since the dummy bump comes into contactwith the wiring member of the second semiconductor substrate by thedummy bump contact step, the wiring member of the second semiconductorsubstrate is exposed in the space defined by the tracing material afterthe dummy bump has been removed. Therefore, when metallic material issupplied into the space defined by the tracing material after the dummybump has been removed so as to form a bump by the metallic materialsupplying step, this bump is electrically connected to the wiring memberof the second semiconductor substrate. In other words, according to thismanufacturing method, a bump can be formed simultaneously when apenetration electrode is formed, and an electrical connection can beestablished between the bump and the wiring member of the secondsemiconductor substrate when the bump is formed.

For example, the tracing material may be an adhesive to bond the frontsurface of the first semiconductor substrate and the one surface of thesecond semiconductor substrate together.

The wiring member of the second semiconductor substrate may include apenetration electrode that penetrates the second semiconductor substratein a thickness direction thereof. In this case, the dummy bump contactstep may include a step of bringing the dummy bump into contact with thepenetration electrode penetrating the second semiconductor substrate.

Thereby, it is possible to obtain a semiconductor device in which thebump of the first semiconductor substrate is electrically connected tothe penetration electrode of the second semiconductor substrate.

A semiconductor device according to a fourth aspect of the presentinvention comprises a first semiconductor chip and a secondsemiconductor chip. The first semiconductor chip includes asemiconductor substrate having a front surface and a rear surface; afunctional device formed on the front surface of the semiconductorsubstrate; a penetration electrode that is electrically connected to thefunctional device, that is disposed in a through-hole penetrating thesemiconductor substrate in the thickness direction beside the functionaldevice, and that establishes an electrical connection between a frontsurface side and a rear surface side of the semiconductor substrate; anda bump that is formed integrally with the penetration electrode and thatjuts from the front surface of the semiconductor substrate. The secondsemiconductor chip includes a wiring member that is formed on onesurface of the second semiconductor chip facing the front surface of thesemiconductor substrate and that is bonded with the bump of the firstsemiconductor chip.

A semiconductor chip manufacturing method according to a fifth aspect ofthe present invention includes a step of forming a front-surface-sideconcave portion in a semiconductor substrate having a front surface anda rear surface, a light emitting element or a light receiving elementbeing formed on the front surface, the front-surface-side concaveportion being formed in the front surface and having a predetermineddepth smaller than a thickness of the semiconductor substrate; a plugforming step of supplying transparent material into thefront-surface-side concave portion and embedding a plug made of thetransparent material in the front-surface-side concave portion; and athinning step of, subsequent to the plug forming step, removing a partof the rear surface of the semiconductor substrate and thinning thesemiconductor substrate so that the thickness of the semiconductorsubstrate becomes smaller than the depth of the front-surface-sideconcave portion and so that the front-surface-side concave portion isformed into a through-hole that penetrates the semiconductor substrate.

According to this invention, a through-hole penetrating thesemiconductor substrate in the thickness direction can be obtained bythe thinning step. A plug made of transparent material is embedded inthe through-hole. The transparent material mentioned here denotesmaterial that can transmit light (which includes invisible light, suchas infrared light, as well as visible light) emitted from the lightemitting element or material that can transmit light (which includesinvisible light, such as infrared light, as well as visible light)having a wave length range that can be received by the light receivingelement.

Therefore, light emitted from the light emitting element formed on thefront surface of the semiconductor substrate can be guided to therear-surface side of the semiconductor substrate through thethrough-hole (waveguide) in which transparent material is embedded, orlight guided from the rear-surface side of the semiconductor substratecan be received by the light receiving element formed on the frontsurface of the semiconductor substrate through the through-hole. Thus, alight signal can be transmitted through the through-hole.

There is a conventional semiconductor device in which an interposer isprovided with an LSI module formed on its one surface and communicateswith a mounting board by a light signal. In this conventionalsemiconductor device, a chip having a light emitting element or a lightreceiving element is provided on the side of the other surface of theinterposer (i.e., on the side opposite the LSI module). This chip andthe LSI module are electrically connected to each other through apenetration electrode provided in the interposer and through aphotoelectrical-signal-transforming driver IC chip mounted on the onesurface of the interposer.

The thus structured conventional semiconductor device has difficulty inachieving a reduction in size, because chips are disposed on both sidesof the interposer.

Since the semiconductor chip produced according to the manufacturingmethod of this invention can send and receive a light signal between thefront-surface side and the rear-surface side of the semiconductorsubstrate through the through-hole, a light signal can be sent andreceived between the light emitting element or the light receivingelement and the mounting board even if this semiconductor chip ismounted on the mounting board in the state of causing the rear-surfaceside of the semiconductor substrate to face the mounting board.

Therefore, it is possible to realize a semiconductor device in whichthis semiconductor chip is used as an interposer, and the LSI module ismounted on the front surface side of the semiconductor substrate, andhence communication by a light signal can be achieved with the mountingboard placed on the side of one surface thereof while having the lightemitting element or the light receiving element and the LSI module onthe side of the other surface thereof. Moreover, thephotoelectrical-signal-transforming driver IC chip, in addition to thelight emitting element or the light-receiving element, can be formed inthe semiconductor substrate (the front surface), not as a chip separatedfrom the semiconductor substrate. Therefore, the semiconductor devicecan be reduced in size.

Additionally, in the conventional semiconductor device having theinterposer, the position accuracy of the chip having the light emittingelement or the light receiving element with respect to the mountingboard depends not only on the mounting accuracy of the chip having thelight emitting element or the light receiving element with respect tothe interposer but also the mounting accuracy of the interposer withrespect to the mounting board. Therefore, it was impossible to enhancethe position accuracy of the chip having the light emitting element orthe light receiving element with respect to the mounting board.

Likewise, there is a signal-processing semiconductor device in which achip having a light emitting element or a light receiving element ismounted on one surface of a substrate having a through-hole, and lightis transmitted between the light emitting element or the light receivingelement and the other-surface side of the substrate through thethrough-hole. In this case, sometimes, light cannot excellently passthrough the through-hole, and a light signal cannot be processed if themounting accuracy of the chip having the light emitting element or thelight receiving element is low with respect to the substrate having thethrough-hole.

According to this invention, since the light emitting element or thelight receiving element can be directly formed in the semiconductorsubstrate, the position accuracy of the light emitting element or thelight receiving element with respect to the semiconductor substrate canbe enhanced. Therefore, when this semiconductor chip is mounted on themounting board, the position accuracy of the light emitting element orthe light receiving element with respect to the mounting board can beenhanced.

Additionally, according to this invention, a semiconductor chipcharacterized in that a through-hole and a light emitting element or alight receiving element are formed in the single chip is produced.Therefore, unlike a case in which a chip having a light emitting elementor a light receiving element is mounted on a substrate having athrough-hole, the mounting accuracy of a chip does not become a problem.That is, according to this manufacturing method, it is possible toproduce a semiconductor chip capable of excellently transmitting a lightsignal through a through-hole formed in a semiconductor substrate.

If three or more semiconductor chips each of which has a light emittingelement or a light receiving element and has no through-hole are stackedtogether, a light signal was unable to be directly transmitted betweentwo semiconductor chips not adjacent to each other.

In contrast, the semiconductor chip produced by this invention cantransmit a light signal through the through-hole, and hence, even whenthree or more semiconductor chips each of which is the one produced bythis invention are stacked together, a light signal can be directlytransmitted between the two semiconductor chips not adjacent to eachother.

This semiconductor chip manufacturing method may further include a stepof forming a member that establishes a light path between the lightemitting element or the light receiving element and the rear surfaceside of the semiconductor substrate through the through-hole beside thelight emitting element or the light receiving element.

Thereby, even when light emitted from the light emitting element is notdirectly guided to the rear surface side of the semiconductor substratethrough the through-hole, the light path between the light emittingelement and the rear surface side of the semiconductor substrate throughthe through-hole can be established by the light path establishingmember. Likewise, even when light guided from the rear surface side ofthe semiconductor substrate through the through-hole is not directlyreceived by the light receiving element, the light path between the rearsurface side of the semiconductor substrate and the light receivingelement through the through-hole can be established by the light pathestablishing member.

A semiconductor chip manufacturing method according to a sixth aspect ofthe present invention includes a step of forming a front-surface-sideconcave portion in a semiconductor substrate having a front surface anda rear surface, a light emitting element or a light receiving elementbeing formed on the front surface, the front-surface-side concaveportion being formed in the front surface and having a predetermineddepth smaller than a thickness of the semiconductor substrate; a dummyplug forming step of supplying a filler into the front-surface-sideconcave portion and embedding a dummy plug made of the filler in thefront-surface-side concave portion; a thinning step of, subsequent tothe dummy plug forming step, removing a part of the rear surface of thesemiconductor substrate and thinning the semiconductor substrate so thatthe thickness of the semiconductor substrate becomes smaller than thedepth of the front-surface-side concave portion and so that thefront-surface-side concave portion is formed into a through-hole thatpenetrates the semiconductor substrate; and a dummy plug removing stepof, subsequent to the thinning step, removing the dummy plug provided inthe through-hole.

According to this invention, when the thinning step is executed, sincethe dummy plug is embedded in the front-surface-side concave portion(through-hole), grinding waste can be prevented from coming into thethrough-hole, for example, even if the thinning step is to physicallygrind the rear surface of the semiconductor substrate.

On the other hand, since the dummy plug embedded in the through-hole isremoved after the through-hole is formed according to the thinning step,light can pass through this through-hole even if the filler does nothave transparency. Therefore, light can be transmitted between the lightemitting element or the light receiving element formed on the frontsurface of the semiconductor substrate and the rear surface side of thesemiconductor substrate through the through-hole.

The semiconductor chip produced according to the manufacturing methodenables a size reduction of a semiconductor device using thissemiconductor chip as an interposer. Additionally, since a light signalcan be transmitted through the through-hole, when three or moresemiconductor chips each of which is the semiconductor chip producedaccording to the manufacturing method are stacked together, the lightsignal can be directly transmitted between two semiconductor chips notadjacent to each other.

Additionally, since the through-hole and the light emitting element orthe light receiving element are formed on the single chip, the mountingaccuracy of the chip does not become a problem, unlike a case in which achip having a light emitting element or a light receiving element ismounted on a substrate having a through-hole. In other words, it ispossible to produce a semiconductor chip capable of excellentlytransmitting a light signal through a through-hole formed in thesemiconductor substrate by this semiconductor chip manufacturing method.

A semiconductor chip according to a seventh aspect of the presentinvention comprises a semiconductor substrate having a front surface anda rear surface; alight emitting element or a light receiving elementformed on the front surface of the semiconductor substrate; and a memberthat establishes a light path between the light emitting element or thelight receiving element and a rear surface side of the semiconductorsubstrate through a through-hole penetrating the semiconductor substratein a thickness direction thereof beside the light emitting element orthe light receiving element.

This semiconductor chip can be produced by executing a step of forming amember that establishes a light path between the light emitting elementor the light receiving element and the rear surface side of thesemiconductor substrate through the through-hole in the semiconductorchip manufacturing method mentioned above.

For example, a member that reflects light emitted from the lightemitting element toward the rear surface side of the semiconductorsubstrate through the through-hole or a member that reflects lightguided from the rear surface side of the semiconductor substrate to thefront surface side of the semiconductor substrate through thethrough-hole toward the light receiving element, such as a prism or amirror, can be used as the light path establishing member.

The aforementioned objects, other objects, features, and advantageouseffects of the present invention will become apparent from the followingdescription of embodiments given with reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic sectional view showing a structure of asemiconductor chip produced by a manufacturing method according to afirst embodiment of the present invention.

FIG. 2A to FIG. 2I are diagrammatic sectional views for explaining themanufacturing method of a semiconductor device shown in FIG. 1.

FIG. 3 is a diagrammatic sectional view showing a structure of asemiconductor chip produced by a manufacturing method according to asecond embodiment of the present invention.

FIG. 4 is a diagrammatic sectional view showing a structure of asemiconductor chip produced by a manufacturing method according to athird embodiment of the present invention.

FIG. 5A to FIG. 5J are diagrammatic sectional views for explaining themanufacturing method of a semiconductor device shown in FIG. 4.

FIG. 6 is a diagrammatic sectional view showing a structure of asemiconductor chip produced by a manufacturing method according to afourth embodiment of the present invention.

FIG. 7 is a diagrammatic sectional view showing a structure of asemiconductor device that includes a plurality of semiconductor chips,one of which is shown in FIG. 4.

FIG. 8 is a diagrammatic sectional view showing a structure of asemiconductor device according to one embodiment of the presentinvention.

FIG. 9A to FIG. 9H are diagrammatic sectional views for explaining themanufacturing method of the semiconductor device shown in FIG. 8.

FIG. 10 is a diagrammatic sectional view showing a structure of asemiconductor chip according to one embodiment of the present invention.

FIG. 11 is a diagrammatic sectional view showing a semiconductor devicein which a semiconductor chip having a light emitting portion and alight receiving portion is used as an interposer and showing a structureof a mounting board on which the semiconductor device is mounted.

FIG. 12A to FIG. 12C are diagrammatic sectional views for explaining themanufacturing method of the semiconductor chip shown in FIG. 10.

FIG. 13A to FIG. 13H are diagrammatic sectional views for explaining aconventional method for manufacturing a semiconductor chip having apenetration electrode.

FIG. 14 is a diagrammatic sectional view showing a conventionalsemiconductor device that sends and receives a light signal and showinga structure of a mounting board on which the semiconductor device ismounted.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a diagrammatic sectional view showing a structure of asemiconductor chip produced by a manufacturing method according to afirst embodiment of the present invention.

This semiconductor chip 1 includes a semiconductor substrate 2 made ofsilicon, for example. A functional device (an active element such as atransistor or a passive element such as a resistor or a capacitor) 3that has a plurality of electrodes is formed on one surface(hereinafter, referred to as “front surface”) of the semiconductorsubstrate 2. A through-hole 4 that penetrates the semiconductorsubstrate 2 in a thickness direction is formed beside the functionaldevice 3.

A hard mask 6 made of, for example, silicon oxide is formed on the frontsurface of the semiconductor substrate 2. The hard mask 6 has an opening6 a and a contact hole 6 b. The opening 6 a is formed in a region wherethe opening 6 a substantially coincides with the through-hole 4 whenviewed perpendicularly to the front surface of the semiconductorsubstrate 2. A predetermined region (one of the electrodes) of thefunctional device 3 appears inside the contact hole 6 b. The width ofthe opening 6 a is slightly smaller than that of the through-hole 4. Onthe side of the front surface of the semiconductor substrate 2, the hardmask 6 slightly juts inward from the edge of the through-hole 4.

A wiring member 11 is formed in a continuous region including theopening 6 a and the contact hole 6 b when viewed perpendicularly to thefront surface of the semiconductor substrate 2. The wiring member 11 isextended from above the hard mask 6 in such a way as to stop up theopening 6 a. The wiring member 11 is electrically connected to thefunctional device 3 by filling the contact hole 6 b therewith.

A front-surface protecting film 13 made of silicon oxide or siliconnitride (Si₃N₄) is formed on the surface of the wiring member 11 and thesurface of the hard mask 6. The front-surface protecting film 13 has anopening 13 a in a predetermined region on the wiring member 11. Theopening 13 a is formed so as to substantially coincide with the opening6 a of the hard mask 6 when viewed perpendicularly to the front surfaceof the semiconductor substrate 2. A bump (projection electrode) 12jutting from the surface of the front-surface protecting film 13 isjoined to the wiring member 11 through the opening 13 a.

A rear-surface protecting film 16 that has an opening 16 a and that ismade of silicon oxide or silicon nitride is formed on a surface(hereinafter, referred to as “rear surface”) opposite the front surfaceof the semiconductor substrate 2. The opening 16 a is formed so as tosubstantially coincide with the through-hole 4 when viewedperpendicularly to the front surface of the semiconductor substrate 2.The inner wall surface of the through-hole 4 and the inner wall surfaceof the opening 16 a are formed continuously.

An insulating film 5 made of silicon oxide (SiO₂) is formed on the innerwall surface of the through-hole 4, the inner wall surface of theopening 6 a, and the inner wall surface of the opening 16 a. Acontinuous diffusion-preventing film 7 made of conductive material, suchas titanium-tungsten (TiW), tantalum nitride (TaN), or titanium nitride(TiN), is formed on the insulating film 5 and on the surface of thewiring member 11 appearing inside the opening 6 a.

The inner region of the diffusion preventing film 7 in the through-hole4 and in the openings 6 a and 16 a is filled with a penetrationelectrode 10 made of, for example, copper. Therefore, the insulatingfilm 5 and the diffusion preventing film 7 are interposed between thepenetration electrode 10 and the semiconductor substrate 2. Thepenetration electrode 10 is electrically insulated from thesemiconductor substrate 2 by means of the insulating film 5. Thediffusion preventing film 7 is made of material by which metal atoms(copper) constituting the penetration electrode 10 can be prevented frombeing diffused to the semiconductor substrate 2.

On the side of the rear surface of the semiconductor substrate 2, eachof the penetration electrode 10, the diffusion preventing film 7, andthe insulating film 5 has an exposed end face substantially flush withthe surface of the rear-surface protecting film 16. The exposed end faceof the penetration electrode 10 serves as a rear-side connection surface10 a used to be electrically connected to other semiconductor chips orto wiring substrates.

The functional device 3 is electrically connected to the bump 12disposed on the front-surface side of the semiconductor substrate 2through the wiring member 11, and is electrically connected to therear-side connection surface 10 a disposed on the rear-surface side ofthe semiconductor substrate 2 through the wiring member 11, through thediffusion preventing film 7, and through the penetration electrode 10.The bump 12 and the rear-side connection surface 10 a are electricallyconnected to each other through the wiring member 11, the diffusionpreventing film 7, and the penetration electrode 10.

Accordingly, an electrical connection can be made from the front-surfaceside of the semiconductor chip 1 (i.e., the front-surface side of thesemiconductor substrate 2) to the functional device 3 through the bump12. Likewise, an electrical connection can be made from the rear-surfaceside of the semiconductor chip 1 (i.e., the rear-surface side of thesemiconductor substrate 2) to the functional device 3 through therear-side connection surface 10 a. The wiring length between thefront-surface side and the rear-surface side of the semiconductor chip 1is shortened by the penetration electrode 10 that penetrates thesemiconductor substrate 2.

Additionally, since the diffusion preventing film 7 is interposedbetween the penetration electrode 10 and the semiconductor substrate 2,copper atoms constituting the penetration electrode 10 are preventedfrom being diffused into the semiconductor substrate 2, so as not todeteriorate the properties of the semiconductor chip 1.

FIGS. 2A to 2I are diagrammatic sectional views for explaining a methodfor manufacturing the semiconductor chip 1 of FIG. 1. A plurality ofsemiconductor chips 1 are produced from a single semiconductor wafer(hereinafter, referred to simply as “wafer”) W . However, only a part ofa piece that corresponds to one semiconductor chip 1 in the wafer W isshown in FIGS. 2A to 2I. The wafer W of FIGS. 2A to 2I has a pluralityof regions, each of which corresponds to the finished semiconductor chip1 shown in FIG. 1, formed tightly in the in-plane direction of the waferW.

A hard mask 6 that is made of, for example, silicon oxide and that hasan opening 6 a in its predetermined part is formed on one surface(hereinafter, referred to as “front surface”) of a semiconductor wafer W(hereinafter, referred to simply as “wafer”) on which the functionaldevice 3 is formed. The opening 6 a is formed such that a region besidethe functional device 3 is exposed in the wafer W.

Thereafter, a front-surface-side concave portion 9 is formed in theregion beside the functional device 3 according to reactive ion etching(RIE) through the opening 6 a of the hard mask 6. The front-surface-sideconcave portion 9 has a predetermined depth (for example, 70 μm) that issmaller than the thickness of the wafer W (i.e., that does not penetratethe wafer W). As a result of the formation of the front-surface-sideconcave portion 9 according to reactive ion etching, thefront-surface-side concave portion 9 has a width slightly greater thanthe width of the opening 6 a. Therefore, the hard mask 6 slightly jutsinward from the edge of the front-surface-side concave portion 9.

Thereafter, a contact hole 6 b by which one of the electrodes of thefunctional device 3 is exposed is formed in the hard mask 6. The contacthole 6 b can be formed by etching the hard mask 6, for example, througha resist film (not shown) that has an opening in a region correspondingto the contact hole 6 b.

Thereafter, an insulating film 5 made of silicon oxide is formed on theexposed surface of the inside of the opening 6 a and of the inside ofthe front-surface-side concave portion 9 according to a CVD (ChemicalVapor Deposition) method. The insulating film 5 can be formed on theexposed surface of the inside of the opening 6 a and of the inside ofthe concave portion 9, for example, by forming a resist film (not shown)having an opening that exposes the opening 6 a and thefront-surface-side concave portion 9, by forming an insulating film onthe whole surface on the front-surface side of the wafer W in thisstate, and by removing the resist film. FIG. 2A shows this state.

Thereafter, the inside of the front-surface-side concave portion 9 andthe inside of the opening 6 a are filled with non-metallic material,such as a polymer, whereby a dummy plug 8 is formed (see FIG. 2B). Theexposed surface of the dummy plug 8 exposed from the opening 6 a and thesurface of the hard mask 6 are substantially flush with each other.

Thereafter, a wiring member 11 is formed in a region ranging from theinside of the contact hole 6 b to the dummy plug 8. To form the wiringmember 11, metallic material is first applied onto the whole surface onthe front-surface side of the wafer W that has under gone the foregoingprocess. The metallic material is filled in the contact hole 6 b, and isbrought into contact with one of the electrodes of the functional device3 exposed at the inside of the contact hole 6 b. Thereafter, a part ofthe metallic material other than a continuous region including theopening 6 a and the contact hole 6 b (i.e., a region corresponding tothe wiring member 11 (see FIG. 1)), when viewed perpendicularly to thefront surface of the semiconductor substrate 2, is removed by an etchingoperation that uses a resist film of a predetermined pattern, thusobtaining the wiring member 11 electrically connected to the functionaldevice 3.

Further, a front-surface protecting film 13 is formed on the wholesurface on the front-surface side of the wafer W that has undergone theforegoing process, i.e., on the hard mask 6 and the wiring member 11. Anopening 13 a is then formed in the front-surface protecting film 13 in aregion on the opening 6 a. A bump 12 joined to the wiring member 11through the opening 13 a is then formed. FIG. 2C shows this state.

Thereafter, the front surface of the wafer W (i.e., the surface on whichthe functional device 3 is formed) is stuck onto a supporter not shown,whereas the rear surface Wr of the wafer W (i.e., the surface oppositethe front surface) is mechanically ground, whereby the wafer W isthinned. As a result, the dummy plug 8 is exposed at the rear surface Wrof the wafer W, and the front-surface-side concave portion 9 is formedinto the through-hole 4 that penetrates the wafer W in the thicknessdirection. FIG. 2D shows this state.

A grinding damage layer that has grinding marks or damage caused whenground exists on the rear surface Wr of the wafer W. To remove thegrinding damage layer, the rear surface Wr of the wafer W is subjectedto dry etching or wet etching by approximately 5 μm. At this time, thedummy plug 8 and the insulating film 5 are hardly etched, and jut fromthe rear surface Wr of the wafer W. FIG. 2E shows this state.

Thereafter, a rear-surface protecting film 16 made of silicon oxide orsilicon nitride is formed on the whole surface on the rear-surface Wrside of the wafer W that has undergone the foregoing process. In thisstate, the projections of the dummy plug 8 and of the insulating film 5jutting from the rear surface Wr of the wafer W are covered with therear-surface protecting film 16.

Thereafter, the rear surface Wr of the wafer W is mechanically ground,so that the end faces of the projections of the dummy plug 8 and of theinsulating film 5 are exposed from the rear-surface protecting film 16.As a result, an opening 16 a that has an inner wall surface contiguousto the inner wall surface of the through-hole 4 is formed in therear-surface protecting film 16. On the side of the rear surface Wr ofthe wafer W, the surface of the rear-surface protecting film 16 is madesubstantially flush with the exposed end face of the dummy plug 8 andthe exposed end face of the insulating film 5 by grinding the rearsurface Wr of the wafer W. FIG. 2F shows this state.

Thereafter, the dummy plug 8 inside the through-hole 4 and the openings6 a and 16 a is removed, for example, byan etching operation that usesan appropriate solvent. As a result, the wiring member 11 is exposed atthe bottom (on the side of the bump 12) of the opening 6 a (see FIG.2G).

Thereafter, the diffusion preventing film 7 is formed on the wholeexposed surface on the side of the rear surface Wr of the wafer W thathas undergone the foregoing process, i.e., the surface of therear-surface protecting film 16, on the inner wall surface (on theinsulating film 5) of the through-hole 4 and the openings 6 a and 16 a,and the surface exposed from the opening 6 a of the wiring member 11.FIG. 2H shows this state.

Further, a seed layer (not shown) made of copper is formed on thediffusion preventing film 7. A copper film 14 is then formed thereon byelectrolytic plating where the seed layer is used as a seed. The copperfilm 14 is formed to fill the inner region of the seed layer therewithinside the openings 6 a and 16 a and the through-hole 4. The copper film14 is also formed on the seed layer (on the diffusion preventing film 7)outside the openings 6 a and 16 a and the through-hole 4. FIG. 2I showsthis state.

Thereafter, a part of the copper film 14, a part of the seed layer, anda part of the diffusion preventing film 7 that lie outside the openings6 a and 16 a and the through-hole 4 are removed by, for example, CMP(Chemical Mechanical Polishing). As a result, the exposed surface (CMPsurface) of the copper film 14 is formed into the rear-side connectionsurface 10 a that is substantially flush with the surface of therear-surface protecting film 16. The remaining part of the copper film14 serves as the penetration electrode 10. Thereafter, the wafer W iscut at predetermined positions so as to produce semiconductor chips 1,one of which is shown in FIG. 1.

At the step of grinding the rear surface Wr of the wafer W (see FIG. 2D)and the step of removing the grinding damage layer (see FIG. 2E)according to the manufacturing method for the semiconductor chip 1described above, the dummy plug 8 made of non-metallic material, such asa polymer, is disposed in the front-surface-side concave portion 9 (thethrough-hole 4), but metallic material, such as copper, is not disposedtherein. Therefore, since metal atoms are never diffused into the waferW from the rear surface Wr thereof at these steps, a semiconductor chip1 that has a semiconductor substrate 2 with less metal contamination canbe obtained. In other words, according to this manufacturing method, asemiconductor chip 1 that has less metal contamination and that exhibitsexcellent properties can be produced while having a penetrationelectrode 10.

Additionally, since there is no fear that metal contamination willaffect the functional device 3, the wafer W can be extremely thinned(for example, less than 50 μm in thickness).

Still additionally, since the wiring member 11 is formed in such a wayas to cover the exposed surface of the dummy plug 8 on the side of thefront surface of the wafer W, the penetration electrode 10 electricallyconnected to the wiring member 11 can be formed by filling the inside ofthe through-hole 4, from which the dummy plug has been removed, withmetallic material. Since the wiring member 11 is electrically connectedto the functional device 3, the penetration electrode 10 electricallyconnected to the functional device 3 can be easily produced according tothis method.

FIG. 3 is a diagrammatic sectional view showing a structure of asemiconductor chip produced by a manufacturing method according to asecond embodiment of the present invention. In FIG. 3, the samereference symbol as in FIG. 1 is given to an element corresponding toeach element of FIG. 1, and a description thereof is omitted.

This semiconductor chip 31 has a connection pattern 32 provided in aregion around the through-hole 4 on the side of the rear surface of thesemiconductor substrate 2. The connection pattern 32 is formedintegrally with the penetration electrode 10, and is made of the samekind of material as the penetration electrode 10, i.e., is made ofcopper. A diffusion preventing film 7 is interposed between theconnection pattern 32 and the rear-surface protecting film 16.

The surface of the connection pattern 32 serves as a rear-sideconnection surface 32 a to obtain an electrical connection with theoutside of the semiconductor chip 31. A bump of another semiconductorchip or an electrode pad formed on a wiring substrate can be joined atan arbitrary position of the rear-side connection surface 32 a. Forexample, in a semiconductor device that has this semiconductor chip 31and the wiring substrate, the rear-side connection surface 32 a and theelectrode pad of the wiring substrate can be connected together by meansof a bonding wire.

In the method for manufacturing the semiconductor chip 1, the connectionpattern 32 can be obtained such that the copper film 14 is first formed(see FIG. 2I), and the copper film 14, the seed layer, and the diffusionpreventing film 7 are partially removed, but an etching operation, forexample, through the resist film is carried out so as to leave apredetermined part around the through-hole 4 without completely removingthe copper film 14, the seed layer, and the diffusion preventing film 7existing outside the openings 6 a and 16 a and the through-hole 4.

FIG. 4 is a diagrammatic sectional view showing a structure of asemiconductor chip produced by a manufacturing method according to athird embodiment of the present invention. In FIG. 4, the same referencesymbol as in FIG. 1 is given to an element corresponding to each elementof FIG. 1, and a description thereof is omitted.

An insulating film 42 made of photosensitive resin, a diffusionpreventing film 43, and a penetration electrode 45 made of copper areprovided inside the through-hole 4 and the opening 6 a of thesemiconductor chip 41. The insulating film 42 is provided on the wholesurface of the inner wall of the through-hole 4 and the opening 6 a. Thepenetration electrode 45 is disposed along the center axis of thethrough-hole 4 in an inner region of the insulating film 42. Thediffusion preventing film 43 is interposed between the insulating film42 and the penetration electrode 45 and between the wiring member 11 andthe penetration electrode 45.

The insulating film 42 is thicker than the insulating film 5 of thesemiconductor chip 1 of FIG. 1. The penetration electrode 45 and thesemiconductor substrate 2 are excellently insulated from each other withthe insulating film 42. Since the diffusion preventing film 43 isinterposed between the penetration electrode 45 and the semiconductorsubstrate 2, copper atoms constituting the penetration electrode 45 areprevented from being diffused into the semiconductor substrate 2, so asnot to deteriorate the properties of the semiconductor chip 41.

On the side of the rear surface of the semiconductor substrate 2, thepenetration electrode 45, the diffusion preventing film 43, and theinsulating film 42 have each an exposed end face substantially flushwith the surface of the rear-surface protecting film 16. The exposed endface of the penetration electrode 45 serves as a rear-side connectionsurface 45 a to make an electrical connection with another semiconductorchip or with a wiring substrate.

FIG. 5A to FIG. 5J are diagrammatic sectional views for explaining themanufacturing method of the semiconductor chip 41 of FIG. 4. In FIGS. 5Ato 5J, the same reference symbol as in FIGS. 2A to 2I is given to anelement corresponding to each element of FIGS. 2A to 2I, and adescription thereof is omitted.

The process ranging from the first step to the step of forming thefront-surface-side concave portion 9 by reactive ion etching isperformed in the same way as the manufacturing method of thesemiconductor chip 1. Subsequent to the concave-portion forming step,the inside of the front-surface-side concave portion 9 and the inside ofthe opening 6 a are filled with photosensitive resin without forming theinsulating film 5 (see FIG. 2A), and a dummy plug 48 made of thisphotosensitive resin is formed (see FIG. 5A).

The photosensitive resin forming the dummy plug 48 has the so-calledpositive photosensitive properties of being insoluble in a predeterminedsolvent and becoming soluble in this predetermined solvent by beingirradiated with light. The surface exposed from the opening 6 a of thedummy plug 48 is made substantially flush with the surface of the hardmask 6.

Thereafter, a resist film 46 (shown in FIG. 5B by the alternate long andtwo short dashes line) that has an opening 46 a at a predeterminedposition is formed on the side of the front surface of the wafer W.Accordingly, in the exposed surface of the dummy plug 48, the outerperipheral region thereof is covered with the resist film 46, and theinner region thereof is exposed at the inside of the opening 46 a.

An inner central part 48 a of the dummy plug 48 along the center axis ofthe through-hole 4 is exposed to light through the opening 46 a of theresist film 46 and becomes soluble in a predetermined solvent, whereasthe outer peripheral part 48 b that has not been exposed to lightremains insoluble in this solvent (see FIG. 5B).

Thereafter, the step of forming the wiring member 11, the front-surfaceprotecting film 13, and the bump 12 is carried out in the same way asthe manufacturing method of the semiconductor chip 1. In the exposedcentral part 48 a of the dummy plug 48, apart appearing at the opening 6a of the hard mask 6 comes into contact with the wiring member 11. FIG.5C shows this state.

Thereafter, the front surface of the wafer W is stuck onto a supporternot shown, and the rear surface Wr of the wafer W is mechanicallyground, whereby the wafer W is thinned. As a result, the dummy plug 48is exposed at the rear surface Wr of the wafer W, and thefront-surface-side concave portion 9 is formed into the through-hole 4that penetrates the wafer W in the thickness direction. FIG. 5D showsthis state.

Thereafter, to remove the grinding damage layer of the rear surface Wrof the wafer W, the rear surface Wr of the wafer W is subjected to dryetching or wet etching by approximately 5 μm. At this time, the dummyplug 48 is hardly etched, and juts from the rear surface Wr of the waferW. FIG. 5E shows this state.

Thereafter, the step of forming the rear-surface protecting film 16 iscarried out in the same way as the manufacturing method of thesemiconductor chip 1. An opening 16 a that has an inner wall surfacecontiguous to the inner wall surface of the through-hole 4 is formed inthe rear-surface protecting film 16. FIG. 5F shows this state.

Thereafter, the exposed central part 48 a of the dummy plug 48 insidethe through-hole 4 and the openings 6 a and 16 a is removed by anetching operation where the predetermined solvent mentioned above isused. As a result, the wiring member 11 is exposed at the bottom (on theside of the bump 12) of the opening 6 a. The remaining part (i.e., theouter peripheral part 48 b) of the dummy plug 48 is formed into theinsulating film 42. FIG. 5G shows this state.

Thereafter, the diffusion preventing film 43 is formed on the whole ofthe exposed surface on the side of the rear surface Wr of the wafer Wthat has undergone the foregoing process, i.e., on the exposed surfaceof the rear-surface protecting film 16, on the exposed surface of theinsulating film 42, and on the surface of the wiring member 11 exposedfrom the opening 6 a. FIG. 5H shows this state.

A seed layer (not shown) made of copper is formed on the diffusionpreventing film 43. Thereafter, the copper film 47 is formed thereon byelectrolytic plating using this seed layer as a seed. The copper film 14is formed in such a way as to fill the inner region surrounded by theseed layer therewith inside the openings 6 a and 16 a and thethrough-hole 4. The copper film 47 is also formed on the seed layer (thediffusion preventing film 43) outside the openings 6 a and 16 a and thethrough-hole 4. FIG. 5I shows this state.

Thereafter, a part of the copper film 47, a part of the seed layer, anda part of the diffusion preventing film 43 that exist outside theopenings 6 a and 16 a and the through-hole 4 are removed by, forexample, etchback. As a result, the exposed surface (the etchbacksurface) of the copper film 47 serves as the rear-side connectionsurface 45 a that is substantially flush with the surface of therear-surface protecting film 16. The remaining part of the copper film47 serves as the penetration electrode 45. Thereafter, the wafer W iscut at predetermined positions into semiconductor chips 41, one of whichis shown in FIG. 4.

Likewise, in the manufacturing method of the semiconductor chip 41, thedummy plug 48 made of photosensitive resin is provided in thefront-surface-side concave portion 9 (the through-hole 4), and metallicmaterial, such as copper, is not provided therein at the step ofgrinding the rear surface Wr of the wafer W (see FIG. 5D) and the stepof removing the grinding damage layer (see FIG. 5E) Therefore, sincemetal atoms are never diffused into the wafer W at these steps, thesemiconductor chip 41 having the semiconductor substrate 2 that hasundergone less metal contamination can be obtained.

A thick insulating film 42 can be formed by thickening the outerperipheral part 48 b not exposed to light at the step of exposing thedummy plug 48 to light (see FIG. 5B). The thickness of the outerperipheral part 48 b not exposed to light can be easily controlled bythe size of the opening 46 a (see FIG. 5B) of the resist film 46. If theinsulating film 5 is formed according to the CVD method in the same wayas the manufacturing method of the semiconductor chip 1, the insulatingfilm 5 may not be formed so thick as to completely cover the inner wallsurface of the through-hole 4 and the inner wall surface of the opening6 a therewith, and hence an insulation failure will be caused. Incontrast, in the manufacturing method of the semiconductor chip 41, theinsulating film 42 thicker than the insulating film 5 according to theCVD method can be easily formed, thus making it possible to form theinsulating film 42 by which electrical insulation is reliablyestablished between the penetration electrode 45 and the semiconductorsubstrate 2.

The step of exposing the dummy plug 48 to light is carried out byseparately forming the resist film 46 as shown in FIG. 5B. Instead, asshown in FIG. 5J, this exposure step may be carried out such that aprojection of the hard mask 6 near the opening 6 a formed in accordancewith the formation of the front-surface-side concave portion 9 underreactive ion etching is used as a mask. As above, at this exposure step,the outer peripheral part 48 b that has a width corresponding to alength projected from the edge of the front-surface-side concave portion9 of the hard mask 6 inward is not exposed to light and remainsinsoluble in a predetermined solvent, whereas the inner central part 48a is exposed to light and becomes soluble in the predetermined solvent.

FIG. 6 is a diagrammatic sectional view showing a structure of asemiconductor chip produced by a manufacturing method according to afourth embodiment of the present invention. In FIG. 6, the samereference symbol as in FIG. 4 is given to an element corresponding toeach element of FIG. 4, and a description thereof is omitted.

This semiconductor chip 51 has a connection pattern 52 provided in aregion around the through-hole 4 on the side of the rear surface of thesemiconductor substrate 2. The connection pattern 52 is formedintegrally with the penetration electrode 45 and is made of the samekind of material as the penetration electrode 45, i.e., is made ofcopper. The diffusion preventing film 43 is interposed between theconnection pattern 52 and the rear-surface protecting film 16.

The surface of the connection pattern 52 serves as a rear-sideconnection surface 52 a to obtain an electrical connection with theoutside of the semiconductor chip 51. A bump of another semiconductorchip, an electrode pad formed on a wiring substrate, a bonding wire,etc., can be joined at arbitrary positions of the rear-side connectionsurface 52 a.

In the manufacturing method of the semiconductor chip 51, the rear-sideconnection surface 52 a can be obtained such that the copper film 47 isfirst formed (see FIG. 5I), and then the copper film 47, the seed layer,and the diffusion preventing film 43 are partially removed, but anetching operation, for example, through the resist film is carried outso as to leave a predetermined part around the through-hole 4 withoutcompletely removing the copper film 47, the seed layer, and thediffusion preventing film 43 existing outside the openings 6 a and 16 aand the through-hole 4.

FIG. 7 is a diagrammatic sectional view showing a structure of asemiconductor device provided with a plurality of semiconductor chips41, one of which is shown in FIG. 4. In FIG. 7, the same referencesymbol as in FIG. 4 is given to an element corresponding to each elementof FIG. 4, and a description thereof is omitted.

This semiconductor device 20 having a BGA (Ball Grid Array) package anda multichip stack structure includes a flat wiring substrate(interposer) 21. A flat solid state device 19, such as a semiconductorchip or a wiring substrate, is stacked on the wiring substrate 21. Aplurality of semiconductor chips (three semiconductor chips in thisembodiment) 41, one of which is shown in FIG. 4, are stacked on thesolid state device 19. A semiconductor chip 15 is stacked on thesemiconductor chips 41. Except that the semiconductor chip 15 does nothave the through-hole 4 (the penetration electrode 45), thesemiconductor chip 15 has the same structure and the same size as thesemiconductor chip 41.

The wiring substrate 21 is made of insulating material and has wires(not shown) provided on its surface or in its inside. Both of thesemiconductor chips 41 and 15 are bonded according to a so-called facedown method in which the surface (the surface on which the functionaldevice 3 is formed) is directed to the solid state device 19.

The bump 12 of one of the semiconductor chips 41 and 15 is bonded to therear-side connection surface 45 a (see FIG. 4) of the othersemiconductor chip 41 between the two adjoining semiconductor chips 41or between the semiconductor chip 41 and the semiconductor chip 15. Agap is formed between the semiconductor chips 41 and 15 and between thesemiconductor chip 41 and the solid state device 19. This gap is sealedup with layer-to-layer sealing material 24 made of resin.

A metallic ball (e.g., solder ball) 22 is bonded onto the other surface(the surface opposite the side of the solid state device 19) of thewiring substrate 21.

The solid state device 19 is smaller than the wiring substrate 21 and isbonded to the substantially central part of the wiring substrate 21 whenviewed perpendicularly to the wiring substrate 21 and to the solid statedevice 19. The semiconductor chips 41 and 15 are smaller than the solidstate device 19 and are bonded to the substantially central part of thesolid state device 19 when the solid state device 19 and thesemiconductor chips 41 and 15 are viewed vertically like a plan view.The semiconductor chips 41 and 15 are substantially equal to each otherin size and shape when viewed from the direction perpendicular to these,and are disposed so as to lie almost exactly on each other.

An electrode pad (not shown) is provided in a region to which the solidstate device 19 is not opposed on the peripheral part of the one surfaceof the wiring substrate 21. This electrode pad is re-wired inside thewiring substrate 21 or on the wiring substrate 21, and is electricallyconnected to metallic balls 22 provided on the other surface of thewiring substrate 21.

An external-connection pad 19P is formed in a region to which thesemiconductor chip 41 is not opposed on the outer peripheral part of theone surface (i.e., the surface opposite the wiring substrate 21) of thesolid state device 19. The electrode pad of the wiring substrate 21 andthe external-connection pad 19P of the solid state device 19 areelectrically connected to each other through the bonding wire 23.

The semiconductor chips 41 and 15, the solid state device 19, thebonding wire 23, and the surface of the wiring substrate 21 on the sideof the solid state device 19 are sealed with sealing resin (moldingresin) 25.

The functional device 3 of each of the semiconductor chips 41 and 15 isconnected to the solid state device 19 through the penetration electrode45 with a short distance therebetween. The semiconductor device 20 canbe mounted on another wiring substrate through the metallic balls 22.

FIG. 8 is a diagrammatic sectional view showing a structure of asemiconductor device according to one embodiment of the presentinvention. In FIG. 8, the same reference symbol as in FIG. 1 is given toan element corresponding to each element of FIG. 1, and a descriptionthereof is omitted.

This semiconductor device 60 includes a plurality of semiconductor chips61 stacked together, and has a BGA package, for example, similar to thatof the semiconductor device 20 of FIG. 7. FIG. 8 shows only twoadjoining semiconductor chips 61.

The semiconductor chip 61 has a bump 62 that penetrates thefront-surface protecting film 13 and that is formed integrally with thepenetration electrode 10, instead of the bump 12 of the semiconductorchip 1 of FIG. 1. That is, the bump 62 is made of the same material(copper) as the penetration electrode 10.

The width of the bump 62 is smaller than that of the opening 6 a of thehard mask 6. An end on the front-surface side of the penetrationelectrode 10 has a flat surface substantially flush with the surface ofthe hard mask 6. A wiring member 11A is bonded to this flat surface ofthe penetration electrode 10. The wiring member 11A is electricallyconnected to the functional device 3 through the contact hole 6 b of thehard mask 6.

If the end of the penetration electrode 10 does not have such a flatsurface and if the width of the bump 62 is almost equal to that of theopening 6 a, the wiring member 1A will come into contact with the sideface of the bump 62, and the contact area between the wiring member 11Aand the bump 62 will become small, thus lowering the connectionreliability. On the other hand, if the wiring member 1A is bonded to theflat surface of the end of the penetration electrode 10 as in thesemiconductor device 60 of FIG. 8, the contact area between thepenetration electrode 10 and the wiring member 11A will become large,and electrical connection reliability will be increased.

The diffusion preventing film 7 is formed on the surface (periphery) ofthe penetration electrode 10 (excluding the rear-side connection surface10 a) and the bump 62. The diffusion preventing film 7 is not interposedbetween the penetration electrode 10 and the bump 62.

The bump 62 juts from the surface of the front-surface protecting film13. The rear-side connection surface 10 a of one semiconductor chip 61is bonded to the bump 61 of another semiconductor chip 61. A gap havinga size that is almost equal to the height of the projection of the bump62 from the front-surface protecting film 13 is formed between the frontsurface of one semiconductor chip 61 and the rear surface of anothersemiconductor chip 61. This gap is filled with an adhesive layer 63 madeof resin. The two semiconductor chips 61 are bonded together with theadhesive layer 63. The adhesive layer 63 is made of, for example, epoxyor acrylic.

FIG. 9A to FIG. 9H are diagrammatic sectional views for explaining themanufacturing method of the semiconductor device 60 of FIG. 8. In FIGS.9A to 9H, the same reference symbol as in FIGS. 2A to 2I is given to anelement corresponding to each element of FIGS. 2A to 2I, and adescription thereof is omitted.

A plurality of wafers W1 and W2 having a plurality of regionscorresponding to the semiconductor chips 61 are used in themanufacturing method of the semiconductor device 60.

First, the process ranging from the first step to the step of formingthe dummy plug 8 with respect to the wafer W1 is carried out in the sameway as the manufacturing method of the semiconductor chip 1 of FIG. 1(see FIG. 2B). Thereafter, a wiring member 11A electrically connected tothe functional device 3 is formed in the same way as the wiring member11 in the manufacturing method of the semiconductor chip 1. It should benoted that the wiring member 11A is formed in such a manner as to covera part (e.g., approximately one-third) of the exposed surface of thedummy plug 8 exposed from the opening 6 a of the hard mask 6.

Thereafter, the front-surface protecting film 13 is formed on the wholesurface on the front-surface side of the wafer W1 that has undergone theforegoing steps, and the opening 13 a is formed in a predeterminedregion of the front-surface protecting film 13. The opening 13 a isformed such that a part not being in contact with the wiring member 11Ais exposed in the dummy plug 8. FIG. 9A shows this state.

Thereafter, a dummy bump 65 that comes into contact with the dummy plug8 through the opening 13 a is formed (see FIG. 9B). The dummy bump 65 isalmost equal in size and shape to the bump 62 of the semiconductor chip61 (see FIG. 8), and juts from the surface of the front-surfaceprotecting film 13. The dummy bump 65 is made of material that can beeasily removed by an etching operation using a suitable solvent. Forexample, the dummy bump 65 is made of the same material as the dummyplug 8. However, the material of the dummy bump 65 may be different fromthat of the dummy plug 8.

Thereafter, a wafer W2 in which regions that correspond to the finishedsemiconductor chips 61 (see FIG. 8) are tightly formed is prepared. Therear surface W2 r of the wafer W2 is then caused to face the frontsurface of the wafer W1, and the dummy bump 65 of the wafer W1 isbrought into contact with the rear-side connection surface 10 a of thewafer W2. The position of the wafer W1 with respect to the wafer W2 isadjusted, for example, by passing a beam of infrared light through thewafer W1 from the rear surface W1 r of the wafer W1 and monitoring theinfrared light reflected by the wafer W2 while ascertaining an alignmentmark placed on the wafer W2.

This step may be carried out in a state in which the front-surface sideof the wafer W2 is stuck onto a supporter. A gap having a size that isalmost equal to the height of the projection of the bump 65 from thefront-surface protecting film 13 is formed between the wafer W1 and thewafer W2.

Thereafter, the gap between the wafer W1 and the wafer W2 is filled withan adhesive, thus forming the adhesive layer 63. If epoxy or acrylic isused for the adhesive layer 63, the adhesive layer 63 can be obtained,for example, by pouring unhardened liquid epoxy or acrylic into the gaptherebetween and then hardening the epoxy or and acrylic. The adhesivelayer 63 is disposed in such a manner as to surround the periphery ofthe dummy bump 65 and trace the dummy bump 65. FIG. 9C shows this state.

Thereafter, the rear surface W1 r of the wafer W1 is mechanicallyground, whereafter the dummy plug 8 is exposed at the rear surface W1 rof the wafer W1, and the front-surface-side concave portion 9 is formedinto the through-hole 4. FIG. 9D shows this state.

Thereafter, the step of forming the rear-surface protecting film 16 iscarried out in the same way as in the manufacturing method of thesemiconductor chips 1 and 41. The opening 16 a that has an inner wallsurface contiguous to the inner wall surface of the through-hole 4 isformed in the rear-surface protecting film 16. FIG. 9E shows this state.

Thereafter, the dummy plug 8 and the dummy bump 65 are removed by anetching operation using a suitable solvent. As a result, an empty area66 in which the internal space of the opening 16 a, the through-hole 4,and the opening 6 a communicates with the space defined by the adhesivelayer 63 is formed. From the fact that the wiring member 11A is formedto be in contact with the dummy plug 8 and from the fact that the dummybump 65 is in contact with the rear-side connection surface 10 a of thewafer W2, the wiring member 11A and the rear-side connection surface 10a of the wafer W2 are exposed in the empty area 66 from which the dummyplug 8 and the dummy bump 65 have been removed. FIG. 9F shows thisstate.

Thereafter, the diffusion preventing film 7 is formed on the wholeexposed surface on the side of the rear surface W1 r of the wafer W1that has undergone the foregoing steps, i.e., the surface of therear-surface protecting film 16 and the inner wall surface of the emptyarea 66 (which includes the rear-side connection surface 10 a of thewafer W2 and the exposed surface of the wiring member 11A) FIG. 9G showsthis state.

A seed layer (not shown) made of copper is then formed on the diffusionpreventing film 7, and the copper film 14 is formed thereon byelectrolytic plating using this seed layer as a seed. The copper film 14is formed in such a manner as to fill the inner region surrounded by theseed layer inside the empty area 66 therewith. The copper film 14 isalso formed on the seed layer (the diffusion preventing film 7) outsidethe empty area 66. FIG. 9H shows this state.

Thereafter, a part of the copper film 14, a part of the seed layer, anda part of the diffusion preventing film 7 that exist outside the emptyarea 66 are removed by, for example, etchback. As a result, the exposedsurface (etchback surface) of the copper film 14 is formed into therear-side connection surface 10 a that is substantially flush with thesurface of the rear-surface protecting film 16. A part of the copperfilm 14 remaining in the opening 16 a, in the through-hole 4, and in theopening 6 a serves as the penetration electrode 10, and a part of thecopper film 14 remaining in the opening 13 a and in the space divided bythe adhesive layer 63 serves as the bump 62 formed integrally with thepenetration electrode 10.

Thereafter, the wafers W1 and W2 are cut at predetermined positions soas to produce the semiconductor device 60 having the semiconductor chips61 stacked together shown in FIG. 8.

In the manufacturing method of the semiconductor device 60, theformation of the bump 62 and the penetration electrode 10, the bondingof the bump 62 with the rear-side connection surface 10 a of the waferW2, and the bonding of the penetration electrode 10 with the wiringmember 11A can be simultaneously achieved by supplying metallic materialinto the empty area 66 penetrating the wafer W1 stacked on the wafer W2.

There is no need to stack the thinned wafer W1 (the semiconductorsubstrate 2) on the wafer W2 (the other semiconductor substrate 2),because the wafer W1 is thinned while being stacked on the wafer W2.

After forming the penetration electrode 10 of the wafer W1, anotherwafer having the same structure as the wafer W1 of FIG. 9B may befurther placed on the rear surface W1 r of the wafer W1 before cuttingthe wafers W1 and W2, and may be provided with the penetration electrode10 and the bump 62 in the same way as the wafer W1. Thereafter, thewafers W1 and W2, and the other wafers having the same structure as thewafer W1 are cut, thus making it possible to produce a semiconductordevice in which the three semiconductor chips 61 are stacked togetherand are electrically connected together.

FIG. 10 is a diagrammatic sectional view showing a structure of asemiconductor chip according to one embodiment of the present invention.In FIG. 10, the same reference symbol as in FIG. 1 is given to anelement corresponding to each element of FIG. 1, and a descriptionthereof is omitted.

This semiconductor chip 71 has a semiconductor substrate 72. Thesemiconductor substrate 72 has a functional device 73 on its one surface(hereinafter, referred to as “front surface”). The functional device 73has a light emitting portion 73L. A hard mask 6 made of silicon oxide isformed on the surface of the semiconductor substrate 72 in such a manneras to cover the functional device 73.

A through-hole 4 that penetrates the semiconductor substrate 72 in itsthickness direction is formed beside the functional device 73. Anopening 6 a is formed in the hard mask 6 in a region substantiallycoinciding with the through-hole 4 when viewed perpendicularly to thesurface of the semiconductor substrate 72. An insulating film 5 made ofsilicon oxide is formed on the inner wall of the through-hole 4 and onthe inner wall of the opening 6 a. The inside of the through-hole 4 andthe inside of the opening 6 a are filled with transparent material(e.g., transparent resin), whereby a penetration waveguide 74 is formed.The transparent material can transmit light (including invisible light,such as infrared light, as well as visible light) emitted from the lightemitting portion 73L.

A surface waveguide 75 made of transparent material (e.g., transparentresin) is provided on the hard mask 6 from above the light emittingportion 73L to the penetration waveguide 74. The surface waveguide 75 isshaped like a trapezoid in the cross-section shown in FIG. 10, and hasslopes, each forming an angle of 45° with the semiconductor substrate 72on the light emitting portion 73L and on the through-hole 4. Aluminum(Al) is deposited on these slopes, whereby mirrors M1 and M2 are formed.

The mirror M1 assumes a posture capable of reflecting a beam of lightemitted from the light emitting portion 73L and guiding the reflectedlight toward the mirror M2. The mirror M2 assumes a posture capable ofguiding a beam of light incident from the mirror M1 toward the rearsurface (i.e., the surface opposite the surface on which the functionaldevice 73 is formed) of the semiconductor substrate 72 through thethrough-hole 4.

Light (a light signal) emitted from the light emitting portion 73L ofthe functional device 73 is transmitted through the hard mask 6, thenproceeds through the surface waveguide 75, is then reflected by themirror M1, is then reflected by the mirror M2, then proceeds to thepenetration waveguide 74 provided in the through-hole 4 from the surfacewaveguide 75, and arrives at the side of the rear surface of thesemiconductor substrate 72 (this light path is shown by arrow L in FIG.10).

Since this semiconductor chip 71 has the through-hole 4 and the lightemitting portion 73L both of which are formed in the single chip, theproblem of the mounting accuracy is never caused, unlike a case in whicha chip having a light emitting element is mounted on a substrate havinga through-hole. In other words, in this semiconductor chip 71, the lightsignal can be excellently sent through the through-hole 4.

If three or more semiconductor chips each of which has the lightemitting portion 73L or a light receiving portion and has nothrough-hole 4 are stacked together, it was impossible to directly sendand receive a light signal between two semiconductor chips that are notadjacent to each other. In contrast, in this semiconductor chip 71, alight signal can be sent through the through-hole 4, and hence it ispossible to stack three or more semiconductor chips 71 together anddirectly send and receive a light signal between two semiconductor chips71 that are not adjacent to each other.

FIG. 11 is a diagrammatic sectional view showing a semiconductor devicein which a semiconductor chip having a light emitting portion 73L and alight receiving portion is used as an interposer and showing a structureof a mounting board on which this semiconductor device is mounted. InFIG. 11, the same reference symbol as in FIG. 10 is given to an elementcorresponding to each element of FIG. 10, and a description thereof isomitted.

A semiconductor chip 71A of this semiconductor device 80 has thesemiconductor substrate 72. The functional device 73 is formed on onesurface (a front surface) of the semiconductor substrate 72. A lightemitting portion 73L and a light receiving portion 73D are formed in theperipheral portion of the functional device 73. An LSI module 82 formedby stacking a plurality of LSI chips 81 together is bonded onto a regionwhich is the center portion of the functional device 73 and in which thelight emitting portion 73L and the light receiving portion 73D are notformed.

Metallic balls 83 used as external-connection material are provided on asurface (a rear surface) of the semiconductor substrate 72 opposite thefunctional device 73.

The semiconductor device 80 is mounted on a surface of the mountingboard 86 having an optical waveguide 85 formed on this surface, with themetallic balls 83 between the semiconductor device 80 and the mountingboard 86. The position of the semiconductor device 80 with respect tothe mounting board 86 is adjusted so that the penetration waveguide 74(the through-hole) of the semiconductor chip 71A is positioned above apredetermined part of the optical waveguide 85. Therefore, the lightemitting portion 73L and the light receiving portion 73D of thesemiconductor chip 71A provided in the semiconductor device 80 can sendand receive a light signal to and from the mounting board 86.

The semiconductor chip 71A has the penetration waveguide 74(through-hole), thereby making it possible to realize the semiconductordevice 80 capable of sending and receiving a light signal to and fromthe mounting board 86 provided on the side of one surface of thesemiconductor chip 71A although the light emitting portion 73L, thelight receiving portion 73D, and the LSI module 82 are provided on theside of the other surface of the semiconductor chip 71A.

FIG. 14 is a diagrammatic sectional view showing a structure of aconventional semiconductor device that sends and receives a light signaland showing a structure of a mounting board on which this semiconductordevice is mounted. In FIG. 14, the same reference symbol as in FIG. 11is given to an element corresponding to each element of FIG. 11, and adescription thereof is omitted.

This semiconductor device 121 has a semiconductor chip 122 that has awire 123 formed on its one surface (front surface) and that is used asan interposer. An LSI module 82 and a plurality of driver IC chips 124for photoelectrical conversion are arranged sidewise in parallel withthe semiconductor chip 122 and are bonded onto the front surface of thesemiconductor chip 122. The LSI module 82 and the driver IC chips 124for photoelectrical conversion are electrically connected togetherthrough the wire 123.

A light emitting chip 126 provided with a light emitting element 125Land a light receiving chip 127 provided with a light receiving element125D are bonded onto a surface (rear surface) of the semiconductor chip122 opposite the wire 123. The light emitting chip 126 and the lightreceiving chip 127 are electrically connected to the LSI module 82 andthe driver IC chips 124 for photoelectrical conversion through thepenetration electrode 128 penetrating the semiconductor chip 122 in thethickness direction and through the wire 123.

Metallic balls 129 used as external-connection material are provided onthe rear surface of the semiconductor chip 122. The height of theprojection of the metallic ball 129 from the rear surface of thesemiconductor chip 122 is greater than the height of the projection ofeach of the light emitting chip 126 and the light receiving chip 127from the rear surface of the semiconductor chip 122.

Thus, the semiconductor device 121 that has no penetration waveguide 74(see FIG. 11) is required to dispose the light emitting chip 126 and thelight receiving chip 127 on the side of the rear surface of thesemiconductor chip 122 (i.e., on the side of the surface opposite theLSI module 82). Therefore, it was difficult to achieve the sizereduction of the semiconductor device.

When the semiconductor device 121 is mounted on the mounting board 86,the position accuracy of the light emitting chip 126 and the lightreceiving chip 127 with respect to the mounting board 86 depends on themounting accuracy of the light emitting chip 126 and the light receivingchip 127 with respect to the semiconductor chip 122 (interposer) anddepends on the mounting accuracy of the semiconductor chip 122 withrespect to the mounting board 86. Therefore, it was impossible toenhance the position accuracy of the light emitting chip 126 and thelight receiving chip 127 with respect to the mounting board 86.

In contrast, as shown in FIG. 11, in the semiconductor device 80, notonly the light emitting portion 73L and the light receiving portion 73Dbut also the driver IC for photoelectrical conversion can be formed inthe semiconductor substrate 72 itself, not as a chip separated from thesemiconductor substrate 72. Since a light signal can be sent andreceived between the side of the front surface and the side of the rearsurface of the semiconductor chip 71A through the penetration waveguide74 (the through-hole), the light emitting portion 73L and the lightreceiving portion 73D can be formed on the side of the front surface ofthe semiconductor chip 71A (the semiconductor substrate 72). Hence, thesemiconductor device 80 can be made smaller in size than thesemiconductor device 121 (see FIG. 14) in which chips are mounted onboth surfaces of the semiconductor chip 122 (interposer) so as to sendand receive a light signal for communication with the mounting board 86.

Additionally, in the semiconductor chip 71A provided in thesemiconductor device 80 of FIG. 11, since the light emitting portion 73Land the light receiving portion 73D can be directly formed on thesemiconductor substrate 72, the position accuracy of the light emittingportion 73L and the light receiving portion 73D with respect to thesemiconductor substrate 72 can be enhanced. In other words, when thissemiconductor device 80 is mounted on the mounting board 86, theposition accuracy of the light emitting portion 73L and the lightreceiving portion 73D with respect to the mounting board 86 is high,because the position accuracy thereof substantially depends only on themounting accuracy of the semiconductor device 80 (the semiconductor chip71A) with respect to the mounting board 86. Therefore, a light signalcan be excellently sent and received between the light emitting portion73L and the mounting board 76 and between the light receiving portion73D and the mounting board 76.

FIG. 12A to FIG. 12C are diagrammatic sectional views for explaining themanufacturing method of the semiconductor chip 71 of FIG. 10. In FIGS.12A to 12C, the same reference symbol as in FIGS. 2A to 2I is given toan element corresponding to each element of FIGS. 2A to 2I, and adescription thereof is omitted.

Although a plurality of semiconductor chips 71 are produced from asingle wafer W, only a part of a piece corresponding to onesemiconductor chip 71 in the wafer W is shown in FIGS. 12A to 12C. Thewafer W of FIGS. 12A to 12C has a plurality of regions, each of whichcorresponds to the finished semiconductor chip 71 shown in FIG. 10,formed tightly in the in-plane direction of the wafer W.

A hard mask 6 that is made of silicon oxide and that has an opening 6 ain its predetermined part is formed on one surface (hereinafter,referred to as “front surface”) of a wafer W on which the functionaldevice 73 is formed. The opening 6 a is formed such that a region besidethe functional device 73 is exposed in the wafer W.

Thereafter, a front-surface-side concave portion 9 is formed in a regionbeside the functional device 73 by reactive ion etching through theopening 6 a of the hard mask 6 in the same way as the manufacturingmethod of the semiconductor chip 1. The front-surface-side concaveportion 9 has a predetermined depth smaller than the thickness of thewafer W. Thereafter, an insulating film 5 made of silicon oxide isformed on an exposed surface inside the opening 6 a and thefront-surface-side concave portion 9 according to a CVD method. FIG. 12Ashows this state.

Thereafter, the inside of the front-surface-side concave portion 9 andthe inside of the opening 6 a are filled with transparent material(e.g., transparent resin, such as transparent polyimide, or glass) so asto form a plug 78 (see FIG. 12B). The surface of the plug 78 exposedfrom the opening 6 a is made substantially flush with the surface of thehard mask 6.

Thereafter, a surface waveguide 75 separately formed is stuck onto thehard mask 6 and onto the plug 78. At this time, the mirror M1 ispositioned above the light emitting portion 73L, and the mirror M2 ispositioned above the front-surface-side concave portion 9 (see FIG.12C).

Thereafter, the front surface of the wafer W is stuck onto a supporter(not shown), and the rear surface Wr of the wafer W (i.e., the surfaceopposite the functional device 73) is mechanically ground, whereby thewafer W is thinned. As a result, the plug 78 is exposed at the rearsurface Wr of the wafer W, and the front-surface-side concave portion 9is formed into the through-hole 4 penetrating the wafer W in thethickness direction.

Thereafter, the wafer W is cut at predetermined positions so as toproduce semiconductor chips 71, one of which is shown in FIG. 10.

In the manufacturing method described above, the inside of thefront-surface-side concave portion 9 and the inside of the opening 6 amay be filled with an opaque nonmetallic filler, instead of thetransparent material, so as to form a dummy plug. If so, the dummy plugcan be exposed at the rear surface Wr of the wafer W by grinding,thereafter the dummy plug can be removed. In this case, it is possibleto obtain a semiconductor chip in which the inside of the through-hole 4is not filled with a filler. Even in this case, a light signal can besent and received through the through-hole 4.

Additionally, when the rear surface Wr of the wafer W is ground,grinding waste never comes into the through-hole 4, because the insideof the front-surface-side concave portion 9 (the through-hole 4) isfilled with the filler.

The present invention is embodied according to the foregoing embodiment,but can be embodied according to other embodiments. For example,aluminum (Al), tungsten (W), chrome, titanium, gold (Au), indium (In),or tin (Sn)-based solder, instead copper, may be used as metallicmaterial to be supplied to the inside of the opening 6 a and to theinside of the through-hole 4. That is, the penetration electrode 10 andthe connection pattern 32 may be made of aluminum, tungsten, chrome,titanium, gold, indium, or tin-based solder.

The step (see FIG. 2I) of filling the inside of the opening 6 a and theinside of the through-hole 4 with metallic material may be carried outaccording to the CVD method, the sputtering method, or themolten-material dipping method. In these cases, the step of forming aseed layer can be omitted.

Without being limited to the BGA package form, the semiconductor devicehaving the semiconductor chips 1, 31, 41, 51, and 61 stacked togethercan have another package form such as SOP (Small Outline Package), QFP(Quad Flat Package), or QFN (Quad Flat Non-leaded Package).

The embodiments of the present invention have been described in detailas above. However, these are merely concrete examples used to clarifythe technical contents of the present invention. Therefore, the presentinvention should not be understood in the condition of being limited tothese examples. The spirit and scope of the present invention arelimited only by the scope of the appended claims.

This application is based on Japanese Patent Application No.2004-241207, filed in the Japan Patent Office on Aug. 20, 2004, theentire contents of which are hereby incorporated by reference.

1. A method for manufacturing a semiconductor chip, comprising: a stepof forming a front-surface-side concave portion in a semiconductorsubstrate having a front surface and a rear surface, a functional devicebeing formed on the front surface, the front-surface-side concaveportion being formed in the front surface and having a predetermineddepth smaller than a thickness of the semiconductor substrate; a dummyplug forming step of supplying nonmetallic material into thefront-surface-side concave portion and embedding a dummy plug made ofthe nonmetallic material in the front-surface-side concave portion; athinning step of, subsequent to the dummy plug forming step, removing apart of the rear surface of the semiconductor substrate and thinning thesemiconductor substrate so that the thickness of the semiconductorsubstrate becomes smaller than the depth of the front-surface-sideconcave portion and so that the front-surface-side concave portion isformed into a through-hole that penetrates the semiconductor substrate;a dummy plug removing step of removing the dummy plug provided in thethrough-hole; and a step of, subsequent to the dummy plug removing step,supplying metallic material into the through-hole and forming apenetration electrode that establishes an electrical connection betweena front surface side and a rear surface side of the semiconductorsubstrate and that is electrically connected to the functional device.2. A method for manufacturing a semiconductor chip according to claim 1,further comprising a step of forming a wiring member that is in contactwith an exposed surface of the dummy plug on the front surface side ofthe semiconductor substrate and that is electrically connected to thefunctional device, the step of forming a wiring member being carried outsubsequent to the dummy plug forming step and being carried out prior tothe dummy plug removing step.
 3. A method for manufacturing asemiconductor chip according to claim 1, wherein the dummy plug formingstep includes a photosensitive resin filling step of filling an insideof the front-surface-side concave portion with photosensitive resinhaving nonconductivity as the nonmetallic material so as to form thedummy plug made of the photosensitive resin, and an exposure step ofexposing the dummy plug to light so that a predetermined outerperipheral part of the dummy plug along a whole inner wall surface ofthe front-surface-side concave portion is insoluble in a predeterminedetching medium and so that a central part of the dummy plug inward fromthe outer peripheral part is soluble in the predetermined etchingmedium, and the dummy plug removing step includes a development step ofremoving the central part of the dummy plug according to etching usingthe predetermined etching medium.
 4. A method for manufacturing asemiconductor device, comprising: a semiconductor chip producing step ofproducing a plurality of semiconductor chips; and a stacking step ofstacking the plurality of semiconductor chips together, thesemiconductor chip producing step including: a step of forming afront-surface-side concave portion in a semiconductor substrate having afront surface and a rear surface, a functional device being formed onthe front surface, the front-surface-side concave portion being formedin the front surface and having a predetermined depth smaller than athickness of the semiconductor substrate; a dummy plug forming step ofsupplying nonmetallic material into the front-surface-side concaveportion and embedding a dummy plug made of the nonmetallic material inthe front-surface-side concave portion; a thinning step of, subsequentto the dummy plug forming step, removing a part of the rear surface ofthe semiconductor substrate and thinning the semiconductor substrate sothat the thickness of the semiconductor substrate becomes smaller thanthe depth of the front-surface-side concave portion and so that thefront-surface-side concave portion is formed into a through-hole thatpenetrates the semiconductor substrate; a dummy plug removing step ofremoving the dummy plug provided in the through-hole; and a step of,subsequent to the dummy plug removing step, supplying metallic materialinto the through-hole and forming a penetration electrode thatestablishes an electrical connection between a front surface side and arear surface side of the semiconductor substrate and that iselectrically connected to the functional device.
 5. A method formanufacturing a semiconductor device, comprising: a step of forming afront-surface-side concave portion in a first semiconductor substratehaving a front surface and a rear surface, a functional device beingformed on the front surface, the front-surface-side concave portionbeing formed in the front surface and having a predetermined depthsmaller than a thickness of the first semiconductor substrate; a dummyplug forming step of supplying nonmetallic material into thefront-surface-side concave portion and embedding a dummy plug made ofthe nonmetallic material in the front-surface-side concave portion; astacking step of stacking the first semiconductor substrate on a secondsemiconductor substrate while causing the front surface of the firstsemiconductor substrate in which the dummy plug is formed to face onesurface of the second semiconductor substrate; a thinning step ofremoving a part of the rear surface of the first semiconductor substratestacked on the second semiconductor substrate and thinning the firstsemiconductor substrate so that the thickness of the first semiconductorsubstrate becomes smaller than the depth of the front-surface-sideconcave portion and so that the front-surface-side concave portion isformed into a through-hole that penetrates the first semiconductorsubstrate; a dummy plug removing step, subsequent to the thinning step,of removing the dummy plug provided in the through-hole; and a metallicmaterial supplying step of, subsequent to the dummy plug removing step,supplying metallic material into the through-hole and forming apenetration electrode that establishes an electrical connection betweena front surface side and a rear surface side of the first semiconductorsubstrate and that is electrically connected to the functional device.6. A method for manufacturing a semiconductor device according to claim5, further comprising a step of, prior to the stacking step, forming adummy bump that juts from the front surface of the first semiconductorsubstrate and that comes in contact with the dummy plug, wherein: thesecond semiconductor substrate includes a wiring member provided on theone surface of the second semiconductor substrate; the stacking stepincluding: a dummy bump contact step of bringing the dummy bump intocontact with the wiring member of the second semiconductor substrate;and a step of disposing tracing material in such a manner as to cover aperiphery of the dummy bump being in contact with the wiring member ofthe second semiconductor substrate, the dummy plug removing stepincluding: a step of removing the dummy bump, and the metallic materialsupplying step including: a step of supplying metallic material to aspace that communicates with the through-hole and that is defined by thetracing material and forming a bump that is formed integrally with thepenetration electrode and that juts from the front surface of the firstsemiconductor substrate.
 7. A method for manufacturing a semiconductordevice according to claim 6, wherein the wiring member includes apenetration electrode that penetrates the second semiconductor substratein a thickness direction thereof, and the dummy bump contact stepincludes a step of bringing the dummy bump into contact with thepenetration electrode penetrating the second semiconductor substrate. 8.A semiconductor device comprising a first semiconductor chip and asecond semiconductor chip, the first semiconductor chip including: asemiconductor substrate having a front surface and a rear surface; afunctional device formed on the front surface of the semiconductorsubstrate; a penetration electrode, being electrically connected to thefunctional device, disposed in a through-hole penetrating thesemiconductor substrate in the thickness direction beside the functionaldevice, the penetration electrode establishing an electrical connectionbetween a front surface side and a rear surface side of thesemiconductor substrate; and a bump being formed integrally with thepenetration electrode and jutting from the front surface of thesemiconductor substrate, the second semiconductor chip including awiring member, being formed on one surface of the second semiconductorchip facing the front surface of the semiconductor substrate, and bondedwith the bump of the first semiconductor chip.
 9. A method formanufacturing a semiconductor chip, comprising: a step of forming afront-surface-side concave portion in a semiconductor substrate having afront surface and a rear surface, a light emitting element or a lightreceiving element being formed on the front surface, thefront-surface-side concave portion being formed in the front surface andhaving a predetermined depth smaller than a thickness of thesemiconductor substrate; a plug forming step of supplying transparentmaterial into the front-surface-side concave portion and embedding aplug made of the transparent material in the front-surface-side concaveportion; and a thinning step of, subsequent to the plug forming step,removing a part of the rear surface of the semiconductor substrate andthinning the semiconductor substrate so that the thickness of thesemiconductor substrate becomes smaller than the depth of thefront-surface-side concave portion and so that the front-surface-sideconcave portion is formed into a through-hole that penetrates thesemiconductor substrate.
 10. A method for manufacturing a semiconductorchip, the method comprising: a step of forming a front-surface-sideconcave portion in a semiconductor substrate having a front surface anda rear surface, a light emitting element or a light receiving elementbeing formed on the front surface, the front-surface-side concaveportion being formed in the front surface and having a predetermineddepth smaller than a thickness of the semiconductor substrate; a dummyplug forming step of supplying a filler into the front-surface-sideconcave portion and embedding a dummy plug made of the filler in thefront-surface-side concave portion; a thinning step of, subsequent tothe dummy plug forming step, removing a part of the rear surface of thesemiconductor substrate and thinning the semiconductor substrate so thatthe thickness of the semiconductor substrate becomes smaller than thedepth of the front-surface-side concave portion and so that thefront-surface-side concave portion is formed into a through-hole thatpenetrates the semiconductor substrate; and a dummy plug removing stepof, subsequent to the thinning step, removing the dummy plug provided inthe through-hole.
 11. A semiconductor chip comprising: a semiconductorsubstrate having a front surface and a rear surface; a light emittingelement or a light receiving element formed on the front surface of thesemiconductor substrate; and a member that establishes a light pathbetween the light emitting element or the light receiving element and arear surface side of the semiconductor substrate through a through-holepenetrating the semiconductor substrate in a thickness direction thereofbeside the light emitting element or the light receiving element.